RAPIDITY OF ACTIVATION IN THE FERTILIZATION 



OF NEREIS. 



H. B. GOODRICH. 



The following experiments were designed as a test of the 

 rapidity of the action of the spermatozoon of Nereis in relation 

 to the initiation of the processes of maturation. The almost 

 instantaneous effect of the contact of the spermatozoon in stimu- 

 lating the formation of the fertilization membrane and, in this 

 case, of the jelly is well known. It is also usually observed that, 

 in the case of those eggs in which maturation follows insemination, 

 that polar-body formation will occur without fail even if later 

 observation shows that no cleavage follows. It might be con- 

 ceived that the continued action of the spermatozoon were 

 necessary to cause maturation. The results outlined below 

 indicate that maturation in Nereis follows almost, if not quite as 

 brief an application of the stimulus as is necessary to initiate the 

 jelly formation. 



The experiments of Lillie ('n) on Nereis limbata showed 

 clearly that the removal of the spermatozoon later than twenty- 

 one minutes after insemination by a process of centrifuging 

 did not interfere with the maturation of the egg. It was, how- 

 ever, found impossible by this method to remove the sperm 

 earlier than twenty -one minutes after fertilization. Various 

 workers have suggested (I am indebted to Dr. Chambers for 

 first calling this to my attention) that the Barbour apparatus 

 for micro-dissection offered a means of removal during this earlier 

 period. The manipulation of the instrument for this p'urpose 

 has proved most successful. The spermatozoon may readily 

 be removed shortly after attachment and with more difficulty 

 later because of the increasing strength of adherence to the 

 egg and the viscidity of the head of the spermatozoon. The 

 viscidity is shown in attempts to remove the spermatozoon at 

 about 35 minutes after insemination. The head, remaining 

 attached in the region of the perforatorium may be extended by 



196 



